304 INFLAMMATION OF THE LUNGS. 



of a rotting tendency. A more extended acquaintance with 

 the art has taught us the true nature and progress of 

 the disease ; but it appears also to have produced a con- 

 viction in the minds of many veterinarians who wavered on 

 the subject, that pleurisy, independent and distinct from 

 inflammation of the lungs, may and occasionally does exist 

 in the horse ; and that therefore, in a systematic point of 

 view, it is proper to consider the various chest affections 

 under distinct heads ; to which also may be added that of 

 pleuro-pneumonia, or inflammation of the lungs and pleura 

 existing at one and the same time ; as no one will deny that 

 this is by far the most usual form of disease. 



INFLAMMATION OF THE SUBSTANCE OF THE LUNGS, OR 

 PNEUMONIA. 



When we consider how totally we have removed the horse 

 from a life of nature to one of art, in which the lungs, more 

 vascular than any other organs, are subjected in an extra- 

 ordinary degree to the extremes of exertion and temperature, 

 we cannot be surprised that they should in a great measure 

 form the seat of acute inflammation. 



Causes. — The predisposition may be looked for in consti- 

 tutional plethora, occasioned by high feeding, hot clothing, 

 stabling with high temperatures, and by accelerated exercise ; 

 all which render the lungs more susceptible to congestion, 

 and less able to resist the effects of it. Among the various 

 causes alternations between heat and cold are probably the 

 most common ; and we have the more reason to believe 

 that it is the alternations themselves which provoke the 

 disorder, as we find that horses bear the extremes of both 

 heat and cold, in different countries, with seeming im- 

 punity. Heat suddenly applied may be supposed to 

 heighten the circulation generally, and produce conges- 

 tion immediately within the lungs. Cold suddenly applied 

 may act instantly also by driving the blood from the skin 

 to the deeper-seated organs. A very fertile source of it is 

 also occasioned by inordinate exercise, as regards quick- 

 ness of progression, which wears out the vital activity of 

 the lungs ; thus it frequently follows severe runs in hunt- 

 ing ; and thus also horned cattle, which are unused to any 

 motion, are liable to it, when they, in a high state of con- 



